Bighorn sheep, date and location not specified | Photo courtesy of Zion National Park, St. George News

SPRINGDALE — Livestock owners and other concerned citizens gathered at Sunny Lee’s barn in Springdale on Tuesday to discuss the recent outbreak of a deadly strain of pneumonia in the Zion bighorn sheep population, and how to prevent it in the future.

Zion wildlife biologist Janice Stroud-Settles spoke about the disease and how local sheep and goat owners can prevent a future outbreak by keeping their domestic livestock from coming in contact with bighorn sheep.

The disease

Bighorn sheep pneumonia is primarily caused by a bacteria called Mycoplasma ovipneumoniae, otherwise known as Movi, which interferes with the mobile defense mechanisms in the lungs. While the bacteria can cause pneumonia itself, it mainly causes other bacteria to invade the lungs.

Symptoms of the disease include coughing, nasal discharge and laziness, but most often the animals are simply found dead. Bighorn sheep coughing sounds similar to a human cough, and all coughing sheep sightings should be reported to Zion National Park at 435-772-0217 or Zion_park_information@nps.gov.

Movi only affects sheep and goats, and is passed easily through nose-to-nose contact. There is no vaccine or cure for bighorn sheep pneumonia and once a herd has been exposed it’s too late to stop it.

A bighorn sheep ewe and her lamb, date and location not specified | Photo courtesy of Zion National Park, St. George News

“I doesn’t just go away. It doesn’t just fade out. It is persistent in populations for decades and decades. It’s here,” Stroud-Settles said.

While the mortality rate is high, and herds experience an average of a 48 percent population decline, sheep can survive the disease. Those who do survive become immune, but ewes do not pass on this immunity to their lambs. Worse still, the surviving ewes are still carriers and can pass Movi to their lambs who often die as a result.

So far, no sheep have died from pneumonia in Zion since the outbreak. Park officials are cautiously optimistic as it appears the sheep are surviving the disease and becoming immune. However, it could still largely impact the herd if only a few lambs survive this spring.

History of bighorn sheep in Zion

In order to fully understand the situation with today’s bighorn sheep, it is important to know the history of the herd in Zion, Stroud-Settles said.

The first written record of bighorn sheep in Zion was in 1933. Sheep sightings then began to decline in the 1940s and 1950s. By 1953 there were no more bighorn sheep in the park.

In 1973 officials reintroduced the sheep to the park and brought in a herd of 12 from the area of Lake Mead and the Desert National Wildlife Refuge. After a few ups and downs, the herd grew to about 75 sheep in 1990, and all the way to 527 in 2015, the most recent official surveillance number to date. Currently, it is estimated that around 800 bighorn sheep reside in the park, which is considered to be peak capacity.

Since the herd has reached capacity, and therefore the point at which natural selection generally kicks in to reduce and control the size of the herd, park biologists were aware that a situation like pneumonia was possible.

To manage the herd size, and reduce the risk of a pneumonia outbreak, the park increased its tracking efforts and relocated 50 sheep to live with and help boost the San Juan County herd in 2017.

Their fears of pneumonia came true July 20 when they discovered the first of two ewes that tested positive for Movi.

The spread

Every Zion bighorn sheep that park biologists tested for Movi since the 1970s has come back negative, so they know that they contracted it from a domestic sheep or goat.

While “old world” domestic sheep are immune to Movi, 60 percent of them are carriers of the bacteria.

Twenty-three Zion sheep are monitored by GPS tracking collars that collect data every two hours as biologists track the animals’ health and behavior. One such behavior is known as foraying, or the act of an animal leaving its herd then returning to it. This occurs more frequently when herds reach their capacity, and Zion has observed its collared sheep foray recently.

Bighorn sheep also tend to be very curious about their domestic counterparts and may try to interact with them.

“It takes one nose-to-nose contact for transmission to happen and then they go back to their main range and they’re spreading disease,” Stroud-Settles said.

Prevention

The only way to prevent the spread of Movi in the future is to keep domestic and wild sheep from interacting. Stroud-Settles recommended several options to local sheep and goat owners to help prevent the spread.

The first and most highly recommended was different fencing. A double fence with 10 meters between, or an electric fence to keep bighorn away from domestic sheep along with regular maintenance is an easy option.

Another option is to rehome sheep and goats and raise a different kind of livestock or replace them those that have been tested Movi-free. However, bighorn sheep can pass Movi back to domestic sheep so the fencing option is still necessary.

If bighorn sheep are seen near domestic sheep, or if a domestic sheep escapes and is lost, Stroud-Settles asked that livestock owners call the park to help find the animal to reduce the risk of it coming in contact with a bighorn sheep.

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About the Author

Mikayla Shoup grew up in the beautiful mountain town of Flagstaff, Arizona. She recently graduated from Northern Arizona University where she worked for the university's newspaper, The Lumberjack, as a features writer, photojournalist and assistant news editor. In her free time, Mikayla loves exploring the outdoors, traveling and playing with her dogs.